import { loadMode } from '../display/mode_state.js';
import { runInOp } from '../display/operations.js';
import { regChange } from '../display/view_tracking.js';
import { Line, updateLine } from '../line/line_data.js';
import { findMaxLine } from '../line/spans.js';
import { getLine } from '../line/utils_line.js';
import { estimateLineHeights } from '../measurement/position_measurement.js';
import { addClass, rmClass } from '../util/dom.js';
import { lst } from '../util/misc.js';
import { signalLater } from '../util/operation_group.js';

// DOCUMENT DATA STRUCTURE

// By default, updates that start and end at the beginning of a line
// are treated specially, in order to make the association of line
// widgets and marker elements with the text behave more intuitive.
export function isWholeLineUpdate(doc, change) {
  return (
    change.from.ch == 0 &&
    change.to.ch == 0 &&
    lst(change.text) == '' &&
    (!doc.cm || doc.cm.options.wholeLineUpdateBefore)
  );
}

// Perform a change on the document data structure.
export function updateDoc(doc, change, markedSpans, estimateHeight) {
  function spansFor(n) {
    return markedSpans ? markedSpans[n] : null;
  }
  function update(line, text, spans) {
    updateLine(line, text, spans, estimateHeight);
    signalLater(line, 'change', line, change);
  }
  function linesFor(start, end) {
    let result = [];
    for (let i = start; i < end; ++i) result.push(new Line(text[i], spansFor(i), estimateHeight));
    return result;
  }

  let from = change.from,
    to = change.to,
    text = change.text;
  let firstLine = getLine(doc, from.line),
    lastLine = getLine(doc, to.line);
  let lastText = lst(text),
    lastSpans = spansFor(text.length - 1),
    nlines = to.line - from.line;

  // Adjust the line structure
  if (change.full) {
    doc.insert(0, linesFor(0, text.length));
    doc.remove(text.length, doc.size - text.length);
  } else if (isWholeLineUpdate(doc, change)) {
    // This is a whole-line replace. Treated specially to make
    // sure line objects move the way they are supposed to.
    let added = linesFor(0, text.length - 1);
    update(lastLine, lastLine.text, lastSpans);
    if (nlines) doc.remove(from.line, nlines);
    if (added.length) doc.insert(from.line, added);
  } else if (firstLine == lastLine) {
    if (text.length == 1) {
      update(firstLine, firstLine.text.slice(0, from.ch) + lastText + firstLine.text.slice(to.ch), lastSpans);
    } else {
      let added = linesFor(1, text.length - 1);
      added.push(new Line(lastText + firstLine.text.slice(to.ch), lastSpans, estimateHeight));
      update(firstLine, firstLine.text.slice(0, from.ch) + text[0], spansFor(0));
      doc.insert(from.line + 1, added);
    }
  } else if (text.length == 1) {
    update(firstLine, firstLine.text.slice(0, from.ch) + text[0] + lastLine.text.slice(to.ch), spansFor(0));
    doc.remove(from.line + 1, nlines);
  } else {
    update(firstLine, firstLine.text.slice(0, from.ch) + text[0], spansFor(0));
    update(lastLine, lastText + lastLine.text.slice(to.ch), lastSpans);
    let added = linesFor(1, text.length - 1);
    if (nlines > 1) doc.remove(from.line + 1, nlines - 1);
    doc.insert(from.line + 1, added);
  }

  signalLater(doc, 'change', doc, change);
}

// Call f for all linked documents.
export function linkedDocs(doc, f, sharedHistOnly) {
  function propagate(doc, skip, sharedHist) {
    if (doc.linked)
      for (let i = 0; i < doc.linked.length; ++i) {
        let rel = doc.linked[i];
        if (rel.doc == skip) continue;
        let shared = sharedHist && rel.sharedHist;
        if (sharedHistOnly && !shared) continue;
        f(rel.doc, shared);
        propagate(rel.doc, doc, shared);
      }
  }
  propagate(doc, null, true);
}

// Attach a document to an editor.
export function attachDoc(cm, doc) {
  if (doc.cm) throw new Error('This document is already in use.');
  cm.doc = doc;
  doc.cm = cm;
  estimateLineHeights(cm);
  loadMode(cm);
  setDirectionClass(cm);
  cm.options.direction = doc.direction;
  if (!cm.options.lineWrapping) findMaxLine(cm);
  cm.options.mode = doc.modeOption;
  regChange(cm);
}

function setDirectionClass(cm) {
  (cm.doc.direction == 'rtl' ? addClass : rmClass)(cm.display.lineDiv, 'CodeMirror-rtl');
}

export function directionChanged(cm) {
  runInOp(cm, () => {
    setDirectionClass(cm);
    regChange(cm);
  });
}
